<h3>1.描述</h3>
<p>响应式表单</p>
<h3>2.示例</h3>
<p>(2.1)单选按钮组测试</p>
<form [formGroup]="buttonGroupForm">
  <ti-button-group formControlName="selected" [items]="items"></ti-button-group>
</form>
